The salmon? Eaten. The days? Shorter. The bears? Fatter. 

After spending the summer eating the fatty pink salmon swimming through Katmai National Park and Preserve in Alaska, it’s time to celebrate the park’s iconic brown bears (Ursus arctos). Fat Bear Week begins on Tuesday, September 22, and here is everything you need to know. 

What is Fat Bear Week?

Think March Madness, just without the basketball and significantly more bears. Fat Bear Week is a single-elimination tournament, where bear enthusiasts from around the world can vote online for their favorite chunky bear. After each round, the bear with the most votes advances until the winner is announced on September 29. According to the Katmai Conservancy, the event began as a one-day event in 2014 with 1,700 votes cast. Only 10 years later, 1.2 million votes were cast from over 100 countries.

The brown bears return to Brooks Falls for the salmon migration every year in late June, where viewers can watch them on explore.org’s livestream. There, they will feast to fatten up for the long winter ahead. By late summer, the nutritious fish will spawn and then begin to die. The bears will then move to the lower Brooks River in September and October to eat the dead and dying salmon near the river’s mouth.

Eating all of this salmon is important because the heftier the bear, the better chance they will survive their long winter hibernation. Despite being the poster species for winter hibernation, bears are not “deep hibernators,” they way that squirrels, bats, and bees are. Bears enter a state called torpor, which is an involuntary state primarily triggered by lack of food. During this time, the bears rely on stored fat reserves for energy. A torpid bear’s eating, drinking, and waste functions will cease, as its body metabolizes these stores it put on over the summer. 

When is Fat Bear Week 2026?

This year, Fat Bear Week begins on Tuesday, September 22, and a winner will be crowned on Tuesday, September 29. 

How can I vote?

Votes may be cast from noon to 9 p.m. EDT (9 a.m. to 6 p.m. PDT and 8 a.m. to 5 p.m. ADT)

from September 22 and 29 at fatbearweek.org.

Photographs comparing the bears from earlier in the summer and later in the summer will be shown, so voters can get an idea of just how much weight the bears put on during their salmon fest. An adult male bear can go from roughly 700 pounds in the early summer to over 1,200 pounds by fall. 

Voters are also encouraged to get familiar with each bear’s life history and the unique challenges they face to survive.

Which bears are competing this year?

The 2026 Fat Bear Week Bracket will be released on Friday, September 18. 

In 2025, Bear #32 (Chunk) took the crown, despite beginning the salmon run with a freshly broken jaw. He was likely injured while fighting with another bear for a mate, but he still managed to catch plenty of fish. Chunk is known for his dominance and size, but also narrow-set eyes, dark fur, a prominent brow ridge, and a distinctive scar across his muzzle. 

How can I support Katmai’s bears?

Donations can be made to Katmai Conservancy’s Otis Fund. The Otis Fund is named after Bear #480 (Otis), who won four Fat Bear Week titles before his death around 2024.  All donations made between September 22 and October 3 will be matched by explore.org. 

What happened with the bears this summer?

This year’s livestream featured an example of how wild (and upsetting to humans) nature can be. On Tuesday, July 28, the live-cams captured a young brown bear cub being killed and eaten by an unrelated mother bear (Bear #806). The deceased cub was born this spring and the child of Bear #909, a 10-year-old brown bear. Bear #909 started the season with two cubs, but now lost both. 

On Sunday, August 2, one of Bear #335’s (Jolly) cubs died, after following three unrelated cubs up a tree. The mother of the cubs already in the tree attacked Bear #335’s cub, who did not survive the encounter. The identity of the mother bear who killed the spring cub was not confirmed. 

Following the first cub’s death, naturalist Mike Fitz and park rangers Christine Loberg and Sarah Bruce said this likely the first documented case occurring at Brooks River. While there is no one answer as to why mother bears are killing cubs, some experts suspect bear adoption, food scarcity, and fights for dominance all play a role. 

Additionally, this year also saw the cub with silver-hued fur, a cub who hopefully learned important lesson about porcupine quill safety, the unique fishing stylings of Bear #164 (Bucky Dent), and Bear #284’s (Electra) family who can “walk on water.”

The post Fat Bear Week kicks off September 22 appeared first on Popular Science.

In the wild, mimicry is an important tool for survival. Some baby hummingbirds disguise themselves as caterpillars with stinging hairs to avoid predators, while octopus, squid, and cuttlefish use camouflage to blend in with their surroundings and hide. Even plants get in on the mimicry fun, with some mimicking the small of rotten meat to attract flies and others using their petals to trick flies into pollinating on them.

True to its name, Iran’s spider-tailed horned viper (Pseudocerastes urarachnoides) has a rather novel strategy. It uses a tail that looks like a spider to lure birds trying to eat the decoy spider. When the time is right, the snake jumps into action and eats the bird. 

The spider-tailed horned viper is a relatively new species to science, and a study published today in the journal The Anatomical Record is peeling back the layers of this master mimic. A team from the Field Museum in Chicago used X-ray computed tomography (XCT) scanners to take a look inside of the snake’s spidery tail and found that their tailbones appear rather normal. 

“Scientists first collected a specimen of this snake in 1968, and when they brought it back to the Field Museum, people thought that it had some sort of deformity at the tip of its tail, like a tumor,” Sara Ruane, a study co-author and the Field’s Associate Curator of Herpetology and Director of the Core Laboratories, said in a statement. “It sat on the shelves of the museum for decades, but it wasn’t until another specimen with a similar tail was found in 2003 that people revisited it.”

Scientists described the snake as a new species in 2006, using the specimen housed in the Field Museum’s collections as the holotype. Holotype specimens serve as a main standard-bearer and reference point for the physical characteristics of a species, so that scientists can compare and contrast them to see if a specimen belongs to one species or another.

Shortly after naming the spider-tailed horned viper, researchers recorded video of the snake using the spider-like appendage at the tip of its tail as a way to lure in unsuspecting birds. 

“I remember being a PhD student in about 2008 and first seeing the videos of this snake in the wild,” says Ruane. “The appendage at the end of its tail is so outrageous, I remember thinking it was so cool. It’s truly unique among snakes.”

In 2023, Ruane attended a conference with Georgios Georgalis, an associate professor at the Polish Academy of Sciences in Kraków. Georgalis mentioned that he was interested in studying the Field Museum’s spider-tailed horned viper holotype specimen. 

“I am primarily a paleontologist, so I try to use modern snake species to make sense of fossil remains,” said Georgalis, who is also a co-author on the new study. “In vipers, the vertebral column unfortunately doesn’t give us very many clues about what kind of snake we’re looking at. When we find fossils, we often just find individual bones rather than the entire skeleton, and the individual vertebrae are so different from each other along the snake’s body that it’s hard to use them to identify a species.”

The spider-tailed horned viper offered a unique opportunity to study snake vertebrae. Georgalis said that viper vertebrae in particular have not been very well studied. They also wanted to know more about this species’ unusual tail.

To take a closer look, they used the Field Museum’s XCT lab. With XCT, scientists can scan objects and take thousands of X-ray images. These images are then stacked together to produce a 3D rendering of the object’s interior. It essentially allows scientists to study rare or one-of-a-kind specimens in detail without cutting them open or and risking damage. 

“With the spider-tailed horned viper, we were particularly interested in seeing what the vertebrae at the tip of the tail look like, because the exterior of this snake’s tail is so unusual, and because it’s used for this unusual bird-luring behavior,” says Georgalis. “In some other snakes, like sand boas and rubber boas, the vertebrae at the tip of the tail have extreme shapes that look really alien. We wanted to investigate if the spider-tailed horn viper’s tail was similarly strange inside.”

Surprisingly, the scans revealed that the inside of the viper’s tail looked quite normal. The spider-tip tail is only visible on the outside of the snake and the vertebrae were the same as they would be in other vipers. 

“There was nothing in the snake’s skeleton that would suggest how extreme its tail looks on the outside,” said Georgalis.

Findings like these show how fossil skeletons only tell one part of the story of what an animal looked like and how it behaved. Nothing in the spider-tailed horned viper’s skeleton would suggest it has such a unique tail, or that the tail twitches in a way that tricks birds. 

“It’s one of the, let’s say, frustrations of the life of a paleontologist,” says Georgalis. “We work with beautiful animals, but most of the time, we’re trying to put together puzzles with some of the pieces missing, and in the end, we can’t be 100% sure of what the animal actually looked like.”

It’s also a reminder that prehistoric life may be even stranger than we can imagine by looking at bones alone. These findings also lay some groundwork for scientists studying how tissues evolve and develop and underscores the value of museum collections.

“Specimens that were collected 50, 100, 200 years ago are still being used all the time to learn new things,” said Ruane.

The post Snake that hunts with fake spider on its tail shocks scientists appeared first on Popular Science.

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Like humans, elephants are famously social creatures. But unlike teenage humans, Asian elephants (Elephas maximus) can think before they act.

Scientists in Thailand discovered this after 16 Asian elephants at the country’s National Elephant Institute successfully participated in a detour test. In this sort of challenge, the animal has to resist an obvious but ineffective strategy (an impulse) to get a treat and follow an effective but indirect alternative—an ability called inhibitory control. 

“Although we are beginning to understand how intelligent elephants are, we still know very little about their capacity for inhibitory control,” Sydney Hope, a postdoctoral researcher at Hunter College in New York, tells Popular Science. “Understanding elephant inhibitory control will help us understand how this aspect of cognition may have evolved across species, including humans. It will also help us understand how elephants may cope with environmental—including anthropogenic—changes.”

In their new study published today in the journal PLOS One, Hope and her colleagues presented Asian elephants with a transparent box filled with fruit. The box also had small holes, so that the elephants could see and smell the goodies inside. The temptation here was to reach directly through the barrier, whose holes were presumably too small for the elephants’ trunk to fit through. The elephants could consistently resist this impulse, and instead used an opening on the side of the box, as they had previously been taught to do. 

In a second version of the trial, the researchers rotated the box. Initially, the elephants gave in to the urge to reach for where the opening used to be, but then rapidly amended their behavior. This fix came slower in older elephants. That’s potentially because of cognitive decline with age, though the team says that further research is necessary on this point. 

More broadly, the study shows that elephants are able to resist an impulsive, ineffective action (like reaching through a perforated, transparent barrier or continuing a no longer successful approach) in favor of e indirect effective behaviors, even if they must change a previously effective strategy. And they’re in good company—inhibitory control is important for humans’ and other animals’ decision-making and cognitive flexibility. For elephants, it might play a significant role in their famous problem-solving and socializing capabilities, according to the researchers. 

“These results may also help conservation efforts,” Hope points out. “One major threat to Asian elephants is human-elephant conflict, often occurring when elephants navigate around barriers (e.g., electric fences) to enter agricultural lands. Understanding how elephants detour around barriers in controlled experiments may help with developing new techniques to mitigate conflict.”

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